Highly alkaline compositions, such as concentrates having a high content of alkaline agents, such as alkali hydroxides, alkaline complexing agents and silicates, and having a pH value above 11, preferably above 13, are frequently used for cleaning of hard surfaces, for mercerization, scouring etc. A good wetting ability combined with a good cleaning effect is essential in the above-mentioned applications, which requires the presence of considerable amounts of suitable surfactants to lower the high surface tension caused by the high amount of electrolytes. It is also important to have a controlled foaming in these systems. To minimize the cost of transportation, these concentrates should contain as small amounts of water and other solvents as possible. It is also advantageous if the concentrates remain homogenous during transportation and storage.
Since these compositions contain high amounts of electrolytes, such as alkali and/or alkaline complexing agents, it is difficult to dissolve larger amounts of surfactants, especially nonionic surfactants. Therefore, in order to improve the solubility, hydrotropes are often added, and the most commonly used hydrotropes are ethanol and sodium xylene or cumene sulphonate. Ethanol is rather efficient, but presents an explosion hazard, and sodium xylene or cumene sulphonate is relatively inefficient at higher surfactant levels. If a surfactant that is soluble in alkaline water solutions without the addition of a hydrotrope is used, there will be a problem with too much foam, which requires the addition of a foam depressor.
Alkyl glycosides have earlier been used in highly alkaline compositions, see for example EP-B1-589 978, EP-A1-638 685 and U.S. Pat. No. 4,240,921. Furthermore, alkyl glycosides are well known as active cleaning agents in commonly used cleaning compositions, see e.g. WO 97/34971, U.S. Pat. No. 4,627,931 and EP-B1-075 995.
EP-B1-589 978 describes the use of C8-C14 alkyl glycosides as surface active auxiliaries in the desizing, bleaching and alkaline scouring of natural and/or synthetic sheet-form textile materials, yarns or flocks, while EP-A1-638 685 relates to a mercerizing wetting agent containing, either alone or in combination, a C4-C18 alkyl glycoside, a C4-C18 alkyl glyconic amide and the corresponding sulphonated derivatives. Liquid highly alkaline cleaning concentrates containing an alkyl glycoside or an alkyl glycidyl ether and surface active nonionic alkylene oxide adducts are described in U.S. Pat. No. 4,240,921. The preferred alkylene oxide adducts are the ones capable of acting as foam depressors, such as polyoxyethylene/polyoxypropylene block copolymers and capped alcohol ethoxylates. The concentrate contains    a) 10-35% by weight of alkali metal hydroxide,    b) 10-50% by weight of a mixture of a first nonionic surfactant which is a polyoxypropylene polyoxyethylene condensate that acts as a foam depressor and a second nonionic surfactant which is a capped ethoxylated alcohol together with an alkyl glycoside or an alkyl glycidyl ether, where the weight ratio between the alkyl glycoside or the alkyl glycidyl ether and the before-mentioned first and second nonionic surfactants is between 5:1 to 10:1 and    c) water to balance.These concentrates are used to formulate low foaming cleaning compositions having utility e.g. in the food industry.
However, the above composition disclosed in U.S. Pat. No. 4,240,921 requires a rather high ratio of alkyl glycoside to the other nonionic surfactants present in the composition. Further, it is well known that the inclusion of larger amounts of PO in an alkoxylate, such as in foam depressors of the Pluronic type, has a negative influence on the biodegradability of the product. Finally, a capped alcohol ethoxylate normally is a poor wetting agent and has in addition a low cleaning ability. Its presence also increases the need for an extra amount of the alkyl glycoside or alkyl glycidyl ether.
There is consequently a need for highly alkaline compositions with improved properties.